In recent years, a navigation device that provides vehicle travel guidance so that a driver can easily reach a desired destination has been often mounted on vehicles. Here, the navigation device is a device that allows to detect a current location of the vehicle by a GPS receiver, etc., obtain map information for the current location through a recording medium such as a DVD-ROM or an HDD or a network, and display the map information on a liquid crystal monitor. In addition, the above-described navigation device has a route search function that searches for, when a desired destination is set, an optimal route from a point of departure (e.g., the current vehicle location) to the set destination, and further has a travel guidance function that provides travel guidance according to the searched route (guided route). In addition, in recent years, there have also been mobile phones, personal digital assistants (PDAs), smartphones, personal computers, etc., that have the same functions as those of the above-described navigation device (hereinafter, referred to as communication terminals including a navigation device).
Here, new roads (newly constructed roads) are constructed all over Japan every year. In addition, along with this, existing roads disappear, intersections are added, or the shapes of existing roads or intersections are changed. At that time, there is a problem that information about newly constructed roads, etc., that are newly constructed after the creation of map information included in a communication terminal is not registered in the map information. Namely, in the communication terminal having map information that does not include newly constructed roads, etc., the newly constructed roads, etc., do not serve as targets for a route search or guidance, and thus, appropriate travel guidance may not be provided, e.g., a roundabout guided route that does not pass through a newly constructed road, etc., is searched for, or roads or intersections that actually exist are not guided on a map image.
Hence, in recent years, there has been proposed a configuration in which a server device having the latest map information performs a route search instead of the communication terminal side, and a guided route is obtained from the server device (hereinafter, referred to as center route search). However, when a center route search is performed, while a route can be searched for based on the latest map information, a problem occurs in which the communication terminal side having an old version of map information cannot appropriately provide travel guidance along a guided route. For example, when a guided intersection at which a left or right turn is to be made in a guided route is a newly constructed intersection, left or right turn guidance at the guided intersection is not provided. In addition, in the case of an intersection whose structure has been changed, guidance in the wrong direction is provided based on old map information.
As means for avoiding the above-described problems upon performing a center route search, for example, JP 2003-77095 A proposes a technique in which, when a server device receives a route search request from a navigation device, while the server device searches for a route, the server device transmits the mesh codes of meshes through which the searched route passes and version information, together with the searched route, to the navigation device, and the navigation device determines, based on the mesh codes and version information transmitted from the server device, whether the version of corresponding mesh data (map information) is older than that of mesh data stored in the server device, and requests the server device for the latest version of mesh data targeted for meshes that have been determined to be old.